Many methods have been utilized to maintain consistent welds within the contact area between the weld gun contact tips and the material to be welded. As the contact tips deteriorate, the contact area increases, resulting in a decrease in the current density at the weld nugget. This results in a decreased heat input and can result in weld defects. Compensation for this decrease in current density over the life of the tips can be accomplished through several different methods to increase or boost the heat. Less heat is required during the first or early stage of the contact tips' life. Once the contact tips have settled in, during a second stage, a gradual increase in heat is required. During the last stage, as the contact tips start to deform, even more heat is required. These three stages form the basis for various weld control programs having a sequence of steps to maintain the integrity of the welds. As an example, some weld controllers employ a manual stepper to adjust for the heat boost, which typically is increased as a series of scheduled linear steps as specified by a weld engineer. Adaptive steppers vary the schedule not only as a function of the number of welds made, but also by a time rate resistance change between the contact tips. The adaptive schedule is based upon an expected normal resistance difference between consecutive weld cycles and will increase the welding current if it is less than a minimum, predetermined value. Another approach has been to use constant current controls, using current limit settings to track a user profile programmed in the stepper control. This tracking action enables the use of current limits established in close proximity to the nominal contact tip or welding current at any point of the user profile, allowing for tighter tolerances. All of these methods have their advantages and disadvantages. One method may be more suitable than another one for a particular type of weld. This could be very critical in high quality, high production resistance weld applications, as would be commonly used for automobile manufacturing applications. In many instances, a production line will have a mixture of weld controllers to take advantage of each welder's best mode of operation for the type of weld required.
Operator interfaces are used to monitor and control the many different type of processes. Weld controllers can have data entry panels for entering different weld schedules, setting parameters, and so on. Monitors can be used to display selected data. These are usually dedicated to a given weld controller or to a network of weld controllers having the same type of control. With a production line having different types of contollers and operator interface units coupled to the same network, it becomes difficult to determine which unit has control of the network as a master or arbitrator of the network and still couple them to a common operator interface control unit for centralized monitoring and control functions because of a mix of dissimilar data structures on the same network. It would be preferrable to have a network operator interface control system coupled to a communications network with only one master in control at a given time and one that is generally adaptable to resistance welders utilizing a variety of control strategies regardless of the types of data handled by each welder.